Jet-cooled laser spectroscopy of the cyclohexoxy radical

Zu, Lily; Liu, Jinjun; Tarczay, György; Dupré, Patrick; Miller, Terry A.

doi:10.1063/1.1701618

Cited by 27 publications

(103 citation statements)

References 29 publications

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“…The averaged experimental value of theÃ −X separation of ethoxy from the photoelectron spectroscopy 17 (20) GHz, |ε ab +ε ba |/2 = 2.65(130) GHz] are adopted from the previous experimental work, 18 the ab initio calculated geometries of ethoxy and isopropoxy are used to derive the momenta of inertial tensor of these two molecules and the unitary transformation matrices U e and U ip . The predicted values are listed in the third column of Table I and compared with the experimental values.…”

Section: Appendix A: Determination Of the Spin-rotation Tensormentioning

confidence: 99%

“…TheÃ −X separations (T 00 ) of the secondary alkoxies 7 and cyclohexoxy 20 were found in DF spectroscopy (also in LIF spectroscopy in the case of cyclohexoxy 20 ) to be smaller than the primary ones (usually <100 cm −1 ). In particular, T 00 was determined to be 68(10) cm −1 for isopropoxy 7 and a more recent determination 21 with higher precision places it at 60.8(1.0) cm −1 .…”

Section: Introductionmentioning

confidence: 99%

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Rotationally resolved ${\tilde{B}} \leftarrow {\tilde{X}}$B̃←X̃ electronic spectra of the isopropoxy radical: A comparative study

Liu

Melnik

Miller

2013

The Journal of Chemical Physics

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112

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The B̃-X̃ laser-induced-fluorescence spectrum of jet-cooled isopropoxy radical (i-C3H7O[middle dot]) has been recorded. Using an isolated state model the observed rotational and fine structure of the origin band has been well simulated to determine rotational constants for both the X̃ and B̃ states and the electron spin-rotation constants of the X̃ state. The line intensities are well simulated with a parallel transition type, requiring the same symmetry for the levels involved of each the X̃ and B̃ state, which confirms the previous suggestion that going from ethoxy (C2H5O[middle dot]) to isopropoxy, the energy ordering of the electron configurations with in- and out-of-plane half-filled p-orbitals of the oxygen atom is reversed and the ground vibronic symmetry changes from a" to a'. However, the observed spin-rotation coupling constants are not consistent with their predication from either semi-empirical theory or quantum chemical calculations. Additionally, the lack of observed transitions involving the out-of-plane transition moment component is not consistent with high level electronic structure calculations suggesting mixing of vibronic levels by strong spin-orbit coupling. A new twofold model has been developed that explicitly includes Coriolis and spin-orbit coupling between different vibronic levels. This model renders the discrepancy between theoretical and experimental spin-rotation constants moot. Moreover, it determines independently the contributions to the observed splitting between the lowest two levels, resulting from non-relativistic kinetic and Coulombic effects, and that due to the relativistic spin-orbit interaction. The experimental values show that these effects are comparable, but that the vibronic one is slightly more important. This result is at variance with state-of-the-art electronic structure calculations which otherwise do a remarkably good job of describing the ground state of isopropoxy.

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Section: Appendix A: Determination Of the Spin-rotation Tensormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rotationally resolved ${\tilde{B}} \leftarrow {\tilde{X}}$B̃←X̃ electronic spectra of the isopropoxy radical: A comparative study

Liu

Melnik

Miller

2013

The Journal of Chemical Physics

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112

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“…This has been observed in DF spectra of all primary and secondary chain alkoxy radicals 25 as well as cyclohexoxy, 7 which was attributed to the large FCFs for such transitions because of the large difference in X/A-and B-state CO bond lengths (ΔR CO ∼ 0.2 Å). When other vibronic bands in the LIF spectra were pumped, DF transitions to the groundstate vibrational level of the same vibrational mode as the pumped band were observed because of large FCFs of such transitions.…”

Section: Discussionmentioning

confidence: 91%

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

et al. 2015

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Vibrational structures of the nearly degenerate X̃ and Ã states of the 2-, 3-, and 4-methylcyclohexoxy (MCHO) radicals were studied by jet-cooled dispersed fluorescence (DF) spectroscopy. The observed transitions were assigned on the basis of vibrational frequencies and Franck-Condon factors predicted by quantum chemical calculations. Intensities of vibronic transitions in the DF spectra are dependent on the laser-induced fluorescence (LIF) bands pumped in the experiment, which can be explained by the difference in geometry and symmetry between the lower X̃/Ã states and the highly excited B̃ state. All three studied isomers of MCHO have close-lying X̃ and Ã states although their energy separations are affected by the position of the methyl group. It is suggested by quantum chemical calculations that the lowest-energy conformers of all three isomers have the half-filled orbital oriented perpendicular to the OCH plane, which is consistent with the observed relative intensities of the B̃ → X̃ and B̃ → Ã origin bands. When the origin and the CO-stretch bands of the B̃ ← X̃ LIF excitation spectra were pumped, the DF spectra were dominated by CO-stretch progressions. When non-CO-stretch vibrational levels of the B̃ state were pumped, progressions of CO-stretch modes combined with the pumped vibrational mode were observed. Excited-state vibrational population relaxation from the CO stretch level to the vibrational ground level and from combination levels of the CO stretch mode and other vibrational modes to the non-CO stretch modes was observed. Analysis of the DF spectra confirms the previous conclusion that all strong LIF bands observed under jet-cooled conditions belong to a single conformer of each positional isomer (Lin et al. RSC Adv. 2012, 2, 583-589).

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“…24,33 The lowest three electronic states X, Ã, and B̃ of alkoxy radicals are well defined in the literature. 26,32,34,35 Its two lowest electronic states can be separated by as low as 61 cm −1 .…”

Section: Alkoxy Radicalsmentioning

confidence: 99%

“…(28598 cm −1 ), B0 (28821 cm −1 ), and C (29058 cm −1 ) are assigned to the origin bands, The cause of the red-shift in the DF spectra within each group has been discussed in our previous publications. 35,93,96 In brief, the large change in the CO bond length upon the B̃ Nevertheless, we assign the A Bands in the experimental LIF spectrum to this conformer based on two facts. First, the calculated (and scaled) origin transition of the GG' conformer matches the frequency of the A0 band.…”

Section: Overview Of Lif and Df Spectramentioning

confidence: 99%

Laster spectroscopic investigations of organic alkoxy and peroxy radicals.

Reza¹

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like to thank the department for having faith in me and admitting me into the Ph.D. program. First, I would like to express my gratitude to my advisor, Jinjun Liu, for his constant guidance and support and for giving me training in science beyond my imagination. His time and patience were really helpful in achieving my goals. I need to also acknowledge my dissertation defense committee members, Dr. Richard J. Wittebort, Dr. Lee Thompson, and Dr. Sergio B. Mendes. Thanks for being there in the key moment of my graduate school career. Next, I have to thank Neil J. Reilly to whom I owe a lot of what I know about the laser-induced fluorescence and dispersed fluorescence system. It was a wonderful experience to work with all the other members of the Liu group, specially Opu, and Hamzeh. I also want to acknowledge the incredible support from the staff, especially Steve, Sherry, Carla, Ben, Jason, and Renu, in the Department of Chemistry. Your kindness and care towards me have been very welcoming during my time here at UofL. v I thank my parents, who always encouraged me and took great pride in my progress in this endeavor. Outside of my lab, I am very much indebted to my dearest friend Dhruba Kumar Pattadar for his timely help and invaluable suggestions during my Ph.D. course work. I am also grateful to my brother and their families for their support and advice in every possible way. My in-laws have stood by me always. I thank them for their encouragement. Finally, I would like to thank my beloved wife, Rumpa, for being with me and her encouragement and support to pursue my Ph.D. degree.

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Jet-cooled laser spectroscopy of the cyclohexoxy radical

Cited by 27 publications

References 29 publications

Rotationally resolved ${\tilde{B}} \leftarrow {\tilde{X}}$B̃←X̃ electronic spectra of the isopropoxy radical: A comparative study

Rotationally resolved ${\tilde{B}} \leftarrow {\tilde{X}}$B̃←X̃ electronic spectra of the isopropoxy radical: A comparative study

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals

Laster spectroscopic investigations of organic alkoxy and peroxy radicals.

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